Superconducting Quantum Interference Devices (SQUIDs) are comprised of tiny loops of superconducting material in which Josephson junctions are placed in the loop path. A Josephson junction is a region of material that provides a weak link between two fully superconducting regions. The direct current (DC) SQUID has two symmetrical Josephson junctions. They are able to sense extremely small magnetic fields. Non-uniforms arrays of DC SQUIDs and DC bi-SQUIDs, which are DC SQUIDs with an additional Josephson junction bisecting the superconducting loop, have been modeled in different array designs and coupling schemes to determine their linearity and sensing capacities and have been fabricated in low temperature superconducting materials. A SQUID-based sensor detects minute magnetic fields and is decoupled from the size of the signals wavelength. Hence the device can sense signals in the DC-GHz range, but still be contained fully on a ˜1×1 cm chip.
SQUID sensors require an electrical current and/or a magnetic flux bias in order to operate. DC SQUIDs are sensitive devices that may be used for measuring vector components and spatial gradients of magnetic fields, as well as an ability to resolve tiny changes in large signals. These features are particularly useful and have already been implemented in many applications such as low-noise amplifiers, biomagnetic research, nondestructive evaluations, and geomagnetic exploration. In order for the SQUID sensor to function while moving some way is needed to mitigate the changes in the earth's magnetic field due to the movement of the sensor.